Preparation And Photocatalytic Activity Of TiO₂ Supported On Mesoporous Silica Molecular Sieve

Heterogeneous photocatalysis by semiconductors has unique advantages in water pollution control, especially in the treatment of wastewater containing poisonous organic compounds which are difficult to destroy. Some commercial TiO₂, especially P-25 (Degussa), in the treatment of exhaust gas and wastewater contaminated with organic and inorganic pollutants has been fully proved. However, their effective applications are hindered by two serious disadvantages. Firstly, small particles trend to agglomerate into large particles, making against on catalyst performance. Secondly, the separation and recovery of catalyst is difficult. For those reasons many researchers have been focused on mesoporous materials supporting titania catalysts, since they do not only take advantage of high surface area but also make the catalyst-recovering stage more facilitation.In this thesis, we have investigated the synthesis of TiO₂/SBA-15 and MSU-1 materials by a post-synthesis step via Ti-alkoxide hydrolysis in the support -isopropanol suspension. The synthesized materials were characterized by X-ray diffraction, nitrogen adsorption, Fourier transform infrared spectroscopy and UV-visible spectroscopy. Photocatalytic activity of the samples has been tested use methylene blue (MB) as the model pollutant and compared with P-25. Mesoporous SBA-15 and MSU-1 both prevent the anatase to rutile phase transformation and the growth of TiO₂ crystal grain. The analyzing results showed that besides the adsorption ability of catalyst, other factors, such as crystal phase, surface area, crystallite size and crystallinity et al, also play an important role in influencing photoactivity. Furthermore there is an optimal ratio of Ti : Si, too high or too low both leading to decrease the photocatalytic activity. Catalyst 30% TiO₂/SBA-15-700℃ has the highest rate constant of 0.0637 min^-1, which is much higher than that of P-25 (0.0297 min^-1). whereas, TiO₂/MSU-1 samples show much lower activity than TiO₂/SBA-15 samples.Titanium substituted mesoporous molecular sieve SBA-15 have been synthesized...